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E-commerce Security
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  1. E-commerce Security Albert Levi Oregon State University Information Security Lab Corvallis, Oregon, USA levi@security.ece.orst.edu Albert Levi, E-commerce security and PKIs

  2. E-commerce • Performing commercial transactions over the Internet • 4 legs • consumer • merchant • consumer’s bank • merchant’s bank Albert Levi, E-commerce security and PKIs

  3. E-commerce 96 Percentage of the Turkish Internet users who are afraid of sending their credit card numbers over the Internet according to daily Milliyet Albert Levi, E-commerce security and PKIs

  4. E-commerce Security • Why? • Everybody says so • They do not trust the Internet • They do not know what is going on at the merchant’s site • They think that some hands are in their wallets • They do not trust people in the process Albert Levi, E-commerce security and PKIs

  5. Security Requirements • Confidentiality • unauthorized parties must not see the data transmitted • Authentication • parties must make sure each other’s identity Albert Levi, E-commerce security and PKIs

  6. Security Requirements • Non-repudiation • nobody should be able to deny sending a message or initiating a transaction later • any possible dispute must be resolved fairly • Integrity • nobody should be able to alter the data while in transit • if altered, that must be sensed Albert Levi, E-commerce security and PKIs

  7. Security Mechanisms • Encryption • encode the data so that only the intended party could decode • For confidentiality Albert Levi, E-commerce security and PKIs

  8. Security Mechanisms • Digital Signatures • a digital information that can be produced only by the sender • The receiver must be able to verify that signature • For authentication, non-repudiation, integrity Albert Levi, E-commerce security and PKIs

  9. Public key Cryptography (PKC) • PKC is the solution to both encryption and digital signatures • One key pair per user • public key • everybody can know it • private key • must be kept secret Albert Levi, E-commerce security and PKIs

  10. PKC - Encryption Alice Bob Albert Levi, E-commerce security and PKIs

  11. PKC - Digital Signatures Alice Bob Albert Levi, E-commerce security and PKIs

  12. Public Key Distribution • Public directories/databases • everybody posts his/her public key • everybody can get others’ public key • everybody can say that “I am Madonna” • Name spoofing problem Albert Levi, E-commerce security and PKIs

  13. Public Key Distribution • There must be a trusted binding between the public key and the identity of its owner • “Digital Certificates” are such bindings • issued by trusted Certificate Authorities (CA) after an identity control Albert Levi, E-commerce security and PKIs

  14. Certificates Certificate Authority (CA) Certified Entity Certificate Issuance Certificate Albert Levi Albert Levi Albert Levi Certificate Verification Verifier Albert Levi, E-commerce security and PKIs

  15. E-commerce Security • Practical solution is SSL (Secure Socket Layer) • Security layer over TCP/IP • mostly for HTTP connections • encrypted and authenticated sessions between web servers and web browsers (clients) • web servers must have certificate • client certificate is optional Albert Levi, E-commerce security and PKIs

  16. Using SSL in E-commerce • By using SSL we can • make sure about the merchant’s name (assuming the CA of the merchant is trusted) • authentication • make sure that nobody can see the traffic (especially the card number) between consumer and merchant • confidentiality Albert Levi, E-commerce security and PKIs

  17. Using SSL in E-commerce • By using SSL we can NOT • provide privacy • merchant sees all information including the card number and name • provide non-repudiation • both parties knows the session key • charge-back cost for merchant’s • guarantee that merchant will behave honestly Albert Levi, E-commerce security and PKIs

  18. Practical Issues on SSL Albert Levi, E-commerce security and PKIs

  19. Practical Issues on SSL Albert Levi, E-commerce security and PKIs

  20. Practical Issues on SSL Albert Levi, E-commerce security and PKIs

  21. Practical Issues on SSL Albert Levi, E-commerce security and PKIs

  22. Using SSL in E-commerce • SSL is not the perfect solution for secure E-commerce • but it is a convenient solution • no need for consumer certificate • just type the card number • minimal change in current business models Albert Levi, E-commerce security and PKIs

  23. SET (Secure Electronic Transaction) • More secure card payment protocol • Efforts started in 1996 by the leadership of Visa and Mastercard • Still not common! Albert Levi, E-commerce security and PKIs

  24. SET (Secure Electronic Transaction) • Secure, but so complex: not convenient • need-to-know • dual signatures • everybody needs certificates • consumers need to register • 5 level PKI • CAs will get a piece from the cake • time consuming PKC operations Albert Levi, E-commerce security and PKIs

  25. A Practical Solution • We need to balance the security vs convenience trade-off • ANSI X9.59 Standard • Standardization effort on Electronic Commerce for Financial Services Industry • Financial Institutions (FIs) will take place of the CAs • AIM: no certificates issued by CAs Albert Levi, E-commerce security and PKIs

  26. ANSI X9.59 Aim • Primary aim is to eliminate Certificate Authority (CA) based digital signatures • CAs are “extra” in the current business models ==> extra cost, complex system • No CA means no change in the current business models ==> no extra cost, simple system Albert Levi, E-commerce security and PKIs

  27. ANSI X9.59 - Basic Characteristics • No consumer certificate • FIs keep the consumer public-keys in their account records • Consumer signature is verified by its FI, not by the merchant • CFI sends an acknowledgment to merchant Albert Levi, E-commerce security and PKIs

  28. ANSI X9.59 - Basic Characteristics • X9.59 does not offer encrypted communication. • Challenging? Here is the justification: • X9.59 uses X9.59-specific PRC (Payment Routing Code) instead of account/card numbers. PRCs are not valid without an accompanying digital signature Albert Levi, E-commerce security and PKIs

  29. ANSI X9.59 - The Model • Outside the scope of X9.59 • mostly part of the current payment infrastructure • a few extra fields are necessary ==> minor modification on the current payment infrastructure Albert Levi, E-commerce security and PKIs

  30. ANSI X9.59 - The Model • “Signed Payment Object” created and signed by consumer to show the intent of payment • contains: hash of the order detail, consumer and merchant PRC values, payment amount and payment details Albert Levi, E-commerce security and PKIs

  31. ANSI X9.59 - The Model • Merchant does NOT check the signature over SigPayObject, • but repacks it as a standard “Authorization Request Object” and sends it to MFI Albert Levi, E-commerce security and PKIs

  32. ANSI X9.59 - The Model • MFI transfers the authentication request to CFI • CFI performs • fund allocation for the transaction • reconstruction of SigPayObject to verify consumer’s signature. CFI uses the public key of the consumer stored in the account records for this verification. Albert Levi, E-commerce security and PKIs

  33. ANSI X9.59 - The Model • CFI responds to MFI with positive or negative acknowledgment Albert Levi, E-commerce security and PKIs

  34. ANSI X9.59 - The Model • MFI forwards this acknowledgment back to the merchant as “Authorization Acknowledgment Object” Albert Levi, E-commerce security and PKIs

  35. ANSI X9.59 - The Model • Merchant signs the authorization response using its private key, • sends it to consumer as “Signed Payment Acknowledgment Object” • This object contains the merchant’s certificate in order to allow the consumer to verify the signature over it Albert Levi, E-commerce security and PKIs

  36. ANSI X9.59 - Two Remaining Problems • Merchant certificates are still in use • X9.59 offers X.509 certificates and a corresponding PKI is necessary • Lack of encryption • No names exist on objects but PRC - consumer/merchant bindings are not secret • Payment amount is sent in cleartext Albert Levi, E-commerce security and PKIs

  37. ANSI X9.59 - Our Approach • X9.59 based e-payment protocol for the Internet • with solution to merchant certificate problem • with optional encryption extensions • COPSEPP (COnvenient and Practically Secure E-Payment Protocol) • our research in going on Albert Levi, E-commerce security and PKIs

  38. COPSEPP • Solution to merchant certificate problem • no pre-generated certificates • MFI sends the merchant’s certificate upon request • Attachments to authorization messages • no extra messages • Only one extra signature is sufficient Albert Levi, E-commerce security and PKIs

  39. COPSEPP Solution to merchant certificate problem • 1 and 2: payment infrastructure authorization messages • 3: AutAckObject • 4: SigPayAckObject Albert Levi, E-commerce security and PKIs

  40. COPSEPP • Optional encryption extensions • between merchant and MFI • easy, they know each other’s public key • between customer and merchant • difficult but possible without extra messages other than the existing authorization messages Albert Levi, E-commerce security and PKIs

  41. COPSEPP - Merchant to Consumer Encryption • 1: payment infrastructure authorization message • 2: AutAckObject Albert Levi, E-commerce security and PKIs

  42. COPSEPP - Consumer to Merchant Encryption • Encrypting SigPayObject • Ongoing research • consumer needs to know Merchant’s PK at the beginning • impossible without using extra message rounds • we think a system where Consumer encrypts the object using CFI’s public key and CFI returns the decrypted object to merchant • no extra messages Albert Levi, E-commerce security and PKIs